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FERMILAC - Fermi LAT Fourth AGN Catalog

 HEASARC
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Overview

This is the third update to the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT). This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of gamma-ray data with energies greater than 50 MeV. The spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The catalog contains includes 3407 AGN located at high Galactic latitudes (|b| > 10 degrees).

Catalog Bibcode

2022ApJS..263...24A

Bulletin

The FERMILAC database table was last updated on 9 June 2023.

References

A full description of the Fourth Fermi LAT AGN Catalog is given in "The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope: Data Release 3" (Ajello et al. 2022, ApJS, 263, 24).

Provenance

This database table was first ingested by the HEASARC in February 2010. It was last updated (to the 4LAC-DR3 version) in June 2023 using electronic data obtained from the Fermi Science Support Center (FSSC). That data is available at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/. Note that this table does not contain the low-latitude sources given in a separate file there, which are not formally a part of the catalog.

Parameters

Name
The source designation, 4FGL JHHMM.m+DDMM, constructed according to the IAU Specifications for Nomenclature, in which the Right Ascension and Declination have been truncated to 0.1 decimal minutes and 1', respectively. The '4' refers to the fourth catalog and 'FGL' represents Fermi Gamma-ray LAT. An 'e' at the end represents an extended source in the 4FGL source catalog.

Data_Release
The data release version: 1 for 4FGL, 2 for new in DR2, 3 for new or changed in DR3.

RA
The Right Ascension of the associated AGN source in the selected equinox. This is given with a precision of 10-4 decimal degrees in the original data.

Dec
The Declination of the associated AGN source in the selected equinox. This is given with a precision of 10-4 decimal degrees in the original data.

LII
The Galactic Longitude of the associated AGN source in decimal degrees.

BII
The Galactic Latitude of the associated AGN source in decimal degrees.

Detection_Significance
The source significance, in units of sigma, over the 50 MeV to 1 TeV band.

Flux_1_100_GeV
The integral photon flux between 1 GeV and 100 GeV, in photon/cm2/s.

Flux_1_100_GeV_Error
The 1-sigma uncertainty on integral photon flux between 1 GeV and 100 GeV, in photon/cm2/s.

Energy_Flux
The energy flux from 100 MeV to 100 GeV, in erg/cm2/s.

Energy_Flux_Error
The 1-sigma uncertainty on energy flux from 100 MeV to 100 GeV, in erg/cm2/s.

Spectrum_Type
The spectral type in the global model (PowerLaw, LogParabola, PLSuperExpCutoff).

PL_Index
The photon index when fitting with the PowerLaw model.

PL_Index_Error
The 1-sigma error on the PowerLaw index.

Pivot_Energy
The energy at which the error on differential photon flux is minimal (decorrelation energy for the PowerLaw fit).

LP_Index
The photon index at pivot_energy when fitting with LogParabola model.

LP_Index_Error
The 1-sigma uncertainty on the LogParabola index.

LP_Beta
The curvature parameter when fitting with the LogParabola model.

LP_Beta_Error
The 1-sigma error on the LogParabola model's curvature parameter.

Analysis_Flags
These flags are the same that used for the corresponding source in the LAT Point Source Catalog. Please refer to the description of the coded values there.

Source_Type
The astrophysical class of the counterpart of the AGN, using the schema given below, where uppercase letters are used to indicate 'identified' counterparts, whereas lowercase letters indicate 'associated' counterparts. 

      agn   = Non-blazar active galaxy
      bcu   = Blazar candidate of uncertain type
      bll   = BL Lac type of blazar
      css   = Compact steep spectrum quasar
      fsrq  = Flat spectrum radio quasar type of blazar
      nlsy1 = Narrow-line seyfert 1
      rdg   = Radio galaxy
      sey   = Seyfert galaxy
      ssrq  = Soft spectrum radio quasar

Assoc_Name
The name of identified or likely associated source.

Assoc_Prob_Bay
The probability of association according to the Bayesian method.

Assoc_Prob_LR
The probability of association according to the Likelihood Ratio method.

Assoc_Catalog
The counterpart catalog driving the association, as taken from one of the following astronomical catalogs: 

     BZCAT (Blazars)                         Massaro et al. (2015)
     BL Lac                                  Véron-Cetty & Véron (2010)
     AGN                                     Véron-Cetty & Véron (2010)
     QSO                                     Véron-Cetty & Véron (2010)
     Seyfert galaxies                        Véron-Cetty & Véron (2010)
     Narrow-line Seyfert galaxies            Berton et al. (2015)
     Narrow-line Seyfert galaxies            Rakshit et al. (2017)
     FRICAT (radio galaxies)                 Capetti et al. (2017a)
     FRIICAT (radio galaxies)                Capetti et al. (2017b)
     Giant Radio Source                      Kuźmicz et al. (2018)
     2WHSP                                   Chang et al. (2017)
     WISE blazar catalog                     D'Abrusco et al. (2014)
     Radio Fundamental Catalog (2019a)       http://astrogeo.org/rfc
     CGRaBS                                  Healey et al. (2008)
     CRATES                                  Healey et al. (2007)
     ATCA 20 GHz southern sky survey         Murphy et al. (2010)

Assoc_RA
The Right Ascension of the associated counterpart in the selected equinox. This is given with a precision of 10-4 decimal degrees in the original data.

Assoc_Dec
The Declination of the associated counterpart in the selected equinox. This is given with a precision of 10-4 decimal degrees in the original data.

Assoc_Error_Radius
The position uncertainy at 95% confidence level of the counterpart localization for assoc_name, in degrees.

VLBI_Assoc_Name
The designation of the Very Long Baseline Interferometry (VLBI) counterpart to the AGN.

Redshift
The redshift of the AGN.

SED_Class
The spectral energy distribution based classification. 

      LSP = Low-synchrotron-peaked (sources with peak frequency < 1014 Hz)
      ISP = Intermediate-synchrotron-peaked (1014 Hz < peak frequency < 1015 Hz)
      HSP = High-synchrotron-peaked (sources with peak frequency > 1015 Hz)

HE_Peak
The energy in the observer frame of the high-energy SED peak, in MeV.

HE_Peak_Error
The 1-sigma error on energy of the high-energy SED peak, in MeV.

HE_nuFnu_Peak
The quantity nu * fnu at the high-energy-peak frequency, in erg/cm2/s.

HE_nuFnu_Peak_Error
The 1-sigma error on spectral energy distribution at high-energy-peak frequency, in erg/cm2/s.

Nu_Syn
The synchrotron-peak frequency in the observer frame, in Hz.

nuFnu_Syn
The quantity nu * fnu at the synchrotron-peak frequency, in erg/cm2/s.

Variability_Index
The sum of the log(likelihood) difference between the flux fitted in each time interval and the average flux over the full catalog interval; a value greater than 18.48 over 12 intervals indicates <1% chance of being a steady source.

Frac_Variability
The fractional variability computed from the fluxes in each year.

Frac_Variability_Error
The 1-sigma uncertainty on exponential index on the fractional variability.

Highest_Energy_Photon
The energy (if greater than 10 GeV) of the highest-energy ULTRACLEANVETO photon with association probability P > 0.95, in GeV.

Contact Person

Questions regarding the FERMILAC database table can be addressed to the HEASARC Help Desk.
Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:27:29 EDT